Vibration apparatus



May 21, 1946. C. LEAVELL ET AL 2,400,550

' VIBRATION APPARATUS Filed Sept. 2, 1941 2 sheets-Sheet `1 Iaf/esleai/ei? Jolz. Heelal' May 2l, 1946. c. LEAVELL E-rAL VIBRATIONAPPARATUS Filed Sept. 2, 1941 2 sheets-sheet 42 conpefssoia f 78 www;

Patented May 21, 1946 UNITED ,STATES PiirrslvrV OFFICE vIBRA'rIoN-APPARATUSl Charles Leavell, Washington, D. C., an'd John A. Wheeler,Princeton, N. J., assignors to Mechanical Research Corporation, acorporation of Pennsylvania Application September Z, 1941, zSerial No.409,306

9 Claims.

the problem in connection with pneumatic orl other percussive tools isthrough the interposition of shock absorbing springs at various pointsbetween the motors of such tools and their handles. Whereassome of thevibrational forces would be dissipated in this manner, the magnitude ofthe objectionable forces is still appreciable, and the physical andnervous reactions upon the operators still excessive.

Pneumatic cushioning has been tried also, as disclosed for example, inthe patentto Noble, 2,061,806, dated November 24, 1936, wherein an aircushion of constant volume is employed. With such construction, arelatively large proportion of the vibrational forces is neverthelesstransmitted to the operator. And in the disclosures of the patents toSimpson et al., 1,221,615, dated April 3, 1917, and Faudi, 1,924,234,dated August 29, 1933, cylinder and piston structures have beeninterposed between the motors and their supporting handles, with.`substantially equal fluid pressures applied to opposite ends of thepistons, whereby the operator is still subjected to a large measure ofthe shock produced.

Springs in 'combination with fluid pressure have been proposed aswel1,.as described in the patent to Collins, 1,792,893, dated February17,

1931, combining the advantages of these systems'.

as well as their disadvantages. 'And another prior art structure seekingto achieve the desired result appears in the patent to Benedict,1,792,888, dated February 17, 1931, wherein there is produced at certaintimes, equalization of the pressures on opposite ends of the pistondeiined by the housing of the' tool motor; and in this constructionthere will likewise be marked variations in the pressure of theentrapped air which constitutes the cushion.

The research resulting in the present invention `has led to a discoverywhichis as startling due to its simplicity asv it is because of itspractical importance. It has been found that if a vibratingbody(exempliiled -by a pneumatic paving breaker) is constrained to floatbetween unequal fluid pressures of lsubstantially constant values, aconstant force can be appliedto a support (handle in the case of thepaving breaker) for the body which will counteract the variable `forcesproducing the vibration so that the vibrat- I ing body can be supportedwithout vibratory forces reaching the support. Thus the deviceaccomplishes the purpose of converting a vibra-4 tory recoil into aconstant force.

The present invention comprises a vibratory body (such as a pneumatictool) related to a support through relatively reciprocable elementsprovided with a suitable seal between them. In this manner, surfacesarranged on opposite sides of` the seal may be exposed to therequiredunequal fluid pressures of substantially constant values. Duringnormal operation of the apparatus, one of the elements assumes aposition intermediate the ends of its stroke as result of theapplication' of a constant force supplementing the lower fluid. pressurein opposition to the higher one.

One practical embodiment of the invention contemplates that thereciprocable elements assume the form of a cylinder and pistonsystem.`lw

Under these conditions, packing rings may constitute the seal and theopposed pressures will be applied to the ends of the piston. One end ofthe piston may be exposed to atmospheric pressure under certaincircumstances, while the other may be subjected to a, subatmosphericpressure. Or, one end may be exposed to superatmospheric pressure whilethe other is presented to atmospheric pressure. Whatever the pressuresources and values may be, they should be unequal and substantiallyconstant. And it should be understood that the difference between theseconstant pressures vmay be changed in various ways to suit conditionsencountered in practice. In the case of a manually operated pneumatictool, the difference in the opposed pressures should be of such valuethat an operator of average size and strength by supplementing the`force of the lower pressure, can overcome the larger one to produce suchrelative movement of the tool and handles as to bring the piston to aposition intermediate the ends of its stroke. In other applications,there will bean added force of some kind to accomplish a similar result.l

' In case a subatmospheric pressure applied to the piston or equivalentelement approaches the zero pressure of a vacuum, then the more nearly aperfect vacuum is maintained, the greater will be the' effect toeliminate the transmission of` vibration to the supporting structure. Insuch a case it is proposed to provide an outwardly opening check valveon the corresponding cylinder end for communication with atmosphereduringV handles.

Typical applications of the invention will be understood more readilywith reference to th attached drawings wherein: i

Fig. 1 is an elevation, partially in section, i1- lustrating one form ofthe invention;

Fig. 2 is a plan of the tool of Fig. l;

Fig. 3 is a sectional elevation illustrating a modied form of theinvention;

Fig. 4 is a section taken along line .4-4 of Fig. 3; and

Fig. 5 is a section taken along line 5-5 of Fig. 3.

As depicted in Figs.- 1 and 2, a pneumatic tool 26 comprising the usualoperating mechanism is supplied with compressed air through an inletpipe 22 and is provided with a suitable exhaust port not shown. From thesides of the tool casing, two or more arms 24 project for a shortdistance, whereupon they are ,bent or otherwise provided with rods 26extending longitudinally of the tool casing and carrying at their endsand the closed ends of the cylinders, despite the I volumetric variationof these chambers in operation. There will then be a. constantsubatmospheric pressure (the substantially vconstant pressure of thevacuum) in these chambers maintained against constant atmosphericpressure by a constant downward force applied to the handles by theoperator. y Should the operator reduce'the force applied to the handles,the piston will move downward towards the lower end of the cylinder.Reversal of the downward force applied by the operator, as by Liftingthe tool by its handles, to

. move it to a new position will result in the piston moving to theextreme lower'end of its stroke due to the weight of the tool,accompanied by opening of check valve 42 should an appreciable quantityof air be entrapped in` the chamber 50. Thus, a new application ofdownward force to the handles will again establish the vacuum wheneverdesired or required.

The modication depictedfin Figs. 3, 4 and '5 is based upon somewhatsimilar principles, but

instead employs a superatmospheric pressure in opposition to thecombination 'of atmospheric pressure and'the force of the operatorapplied tothe tool handles. In this case the tool 20 has been shown ashaving a packed upper end v 52 and an enlarged lower end 54l received ina vsuitable packed pistons 28. These pistons are reciprocably receivedin closely tting cylinders 30 carried by a supportingl assemblycomprising a shield 3 2 andv handles 34. The pistons may be said tofloat in the cylinders since they vare unrestricted except for theprovision of stops to prevent separation of the elements. The pneumatictool together with its pistons and rods is Vrelatively] movablewitl1.respect to the cylinder and/shield assembly. At their upper ends,the cylinders are provided with resilient b1 unpers 36 which may b eheld in position by threaded spiders A38 whichprovide central bushings39 for guiding the rods 26 and the lower ends ofthe cylinders arelikewise provided with resilient bumpers 40 suitably held in position.As shown in Figs. 1 and 2 the upper ends of the cylinders are eX- posedto atmospheric pressure lwhile\the lower ends are provided withoutwardly opening check valves 42 to permit the expulsion of anyentrapped air when the pistons are pushed downwardly.

The admission of air from the supply pipe 22 is controlled by a valve 44of the usual type,

By inter-` connecting the handle and the tool through such a flexiblecable, there will be no interference with the relative movement of theparts.

cylinder 56 whose lower end is open to atmosphere and whose reducedupper end is closed by a cap 58. The body 60 of the tool below thepacked end is shown as provided with a pair of bearing elements 6|engaging the wall of the cylinder 56, with slots 62 between them forcooperation with threaded pins'- 64 which prevent relative rotation ofthe'tool with respect to the cylinder and serve to impose desired limitsupon the longitudinal vmovement of the tool within the cylinder. In'some cases, the ends of the pins received in the slots may be providedwith soft resilient rings 66such-as rubber, for the re'duction of noiseand shock. The entire casing or` cylinder 56 below the piston 52 ismaintained In operation, still considering the form shown.

in Figs. 1 and 2, an operator will apply the tool to the work and beardown upon the handles Q 34 with sufcient force to move the pistons withrespectto their cylinders to an intermediate position of their stroke,such as has :been depicted in Fig. 1v of the drawings. Depression of thelever 48 will then` admit air to the tool andv itsoper` ation willbegin. By moving the pistons to the lpositions shown, the zero pressureof a vacuum will be approached suiciently to establish a sub- `atatmospheric pressure by suitablyventing it with slots 61 defined betweenwebs 68.

'I'h'e supply of air in this form of the invention is delivered from arelatively large tank 68 or other source .of substantially constantpressure through a hose line. 'l0 and a port 12 into the chamber 14dened at the upper end of the cylin-4 der between the cap 58 and piston52. The diameters of the hose line and port are sufficiently large inrelation to the diameter of said chamber so that despite movement ofpiston 52 in the chamber, the pressure therein will remain approximatelyequal to the pressure in the supply tank, and'will therefore provide asubstantially constant force to be overcome at thehandles. A valve stem'I6 projecting from the upper end of the tool is depressible byactuating the lever 48 mounted on one of the handles through a Bowdenwire 46. 'I'he tank 68 is shown as receiving its supply of compressedair from a pump 18 which values to suit the tool, type of-work andoperator.

Since the lower end of the cylinder is open to A atmosphere, it isrequired in this construction that the force applied to the handles bythe operator.

stantially constant pressure in the chambers 56 defined between thelower ends of the pistons.

plus the force of atmosphere, overcome the force of the supplied air tomove the piston structure to a point, intermediate its stroke such ashas been depicted in Fig. 3 of the drawings.

By the expression substantially constant as applied to the forces andpressures set forth'in such a degree of constancy as will sensiblyreduce vibration in a particular system to which the invention isapplied, in accordance with the same principles as apply to the completeelimination cf vibration where absolutely constant values areobtainable. In those cases in which' subatmospheric pressures are used,as a perfect vacuum is approached, small pressure differences willnaturally represent large pressure ratios. In order to clarify the useof terms as much as Possible, in the description and claims hereinvolved, where substantially constant forces and pressures are alludedto, differences in such values, not ratios, are the criteria.

Whereas but two examples of the present invention h'ave been illustratedand described, it will be evident that it is applicable to many uses notspecically mentioned and many forms of construction not depicted inthedrawings. The real scope of the invention will be measured therefore bythe following claims.

We claim: 1. In combination with a vibratory body and a supporttherefor, a vibration converter comprising piston and cylinderstructurerelating said body and support, means for imparting to saidpiston a position intermediate the ends of its tool, means providing aseal between said piston and cylinder means, and means maintaining 4theopposed ends of said piston means at unequal fluid pressures ofsubstantially constant values, one of said pressures being atmospheric.

5. In combination with a vibratory body and a support therefon'avibration converter compris- .ing piston and cylinder structure relatingsaid stroke for normal operation of said body.

stroke during normal operation of said body,

means providing a. seal for said piston with respect to said cylinder,and means maintaining the opposed ends of said piston atlunequal iluidpressures of substantially constant values, one of said iiuid pressuresbeing atmospheric.

2. In combination .with a vibratory body and a support therefor, avibration converter comprising piston and cylinder structure relatingsaid body and support, means for imparting to said piston a positionintermediate the ends of its stroke during normal operation of saidbody, means providing a seal for said piston with respect to saidcylinder, means for establishing iluid pressures at the ends of saidcylinder, and said piston in said intermediate position having itsopposed ends exposed to unequal iluid pressures of substantiallyconstantv values, one of said fluid pressures being subatmospheric.

3. In combination with a vibratory body and a support therefor, a.vibration converter comprising piston and cylinder structure relatingsaid body and support, means for imparting to said body and support,means providing a seal forv said piston wth'respect Ato said cylinder,means maintaining the opposed ends of said piston at unequal fluidpressureslof substantially constant values, and means for applying aforce in opposition to the greater of said iluid pressures to move saidcylinder and thereby to impart piston a position intermediate the endsof its one .of said pressures being atmospheric.-

6. In combination with a pneumatic toolv and v a supporting casingtherefor, avibration converter comprising a housing for said tooldefining a piston and a cylinder dened by said casing for reciprocablyreceiving said piston,

ing and thereby imparting to said tion intermediate the ends of itsstroke for.nor' mal operation of said tool. piston packing formaintaining a seal between the opposite ends of Said piston, and meansmaintaining the opposed ends of said piston at unequal fluid pressuresof substantially constant values, one of said pressures beingatmospheric.

'1.- In combination with a vibratory implement and a support therefor, adevice comprising a cylinder receiving a piston interconnecting saidimplement with its support, means for imparting to said piston aposition intermediate the ends of said cylinder during operation of saidimplement. meansV for establishing nuid pressures-at the ends of saidcylinders, said piston having an end normally exposed to atmosphericpressure,

piston a position intermediate the ends of its l stroke during normaloperation of said body,

casing receiving reciprocable piston means pro-l vided by said tool, ingfor moving said ing to said piston means a the ends of its stroke fornormal handles carried by said cascasing and thereby impartpositionintermediate operation of said means providing a seal for saidpistonwith re- I mospheric.

and another enddeidning with said cylinder a chamber at subatmosphericpressure.

8. In combination with a vibratory implement and a support therefor, avibration converter comprising piston and cylinder articulating meansrelating said implement and support, said cylinder having one end inconstant communication with atmosphere and the other end provided withan outwardly opening relative movement oi' said piston in one directioncreates a vacuum in said other end of the cylinder, and means forapplying a force to said combination for creation of said vacuum.

9. In combination with a vibratory body and a support therefor, ingpiston and cylinder structure body and support. said piston being freelyiloating in said cylinder and a position intermediate the ends ofoperation of said body, means providing a seal for said piston withrespect to said cylinder, and means maintaining the ton at unequal"iluid pressures ot substantially constant values, one of said pressuresbeing at- CHARLES'LEAVEIL. 1 JOHN A.

to saidl handles y projecting from said casing for moving said casipiston a posicheck valve, whereby a vibration converter compris-4relating saidv its stroke duringnormal

